The present invention relates to a compound having oxetanyl group which is utilizable for various reactions such as ring-opening polymerization and addition reaction, a process for producing the compound, and a curing composition comprising the compound. The compounds having oxetanyl group are useful in the fields of coating for wood, coating for metals and printing, for example, as ultraviolet-curing compositions which cure upon irradiation with ultraviolet rays.
The ultraviolet-curing of resins is utilized in the fields of coating for wood, coating for metals and printing taking advantage of high curing rate, good operability with requiring no solvents and very small energy quantity needed.
In the initial development in these fields, the research has been focused on ultraviolet ray-initiating radical polymerizable compounds such as polyfunctional acrylates and unsaturated polyesters, and, consequently, curing compositions comprising polyfunctional acrylates and unsaturated polyesters have been widely used.
Even at present, most of these researches are directed to ultraviolet ray-initiating radical polymerization, but it has been recognized that photo-initiating ionic polymerization is also fairly promising in many fields of application.
That is, since various monomers can be used in photo-initiation ionic polymerization, there is the possibility that cured products having various chemical and physical characteristics are obtained, and epoxy resins having an oxirane ring which are 3-membered cyclic ethers are investigated as the photo-initiation cationic polymerizable compounds. As a result, various curing compositions comprising epoxy resins are proposed. These photo-curing epoxy resins are excellent in properties such as adhesion, heat resistance and chemical resistance.
However, conventional photo-curing epoxy resins have the problem of low photo-curing rate. Therefore, they cannot be used for the uses such as coating for paper and plastics which requires rapid photo-curing. Accordingly, it is earnestly desired to improve curing rate with taking advantage of the characteristics of epoxy resins.
On the other hand, it is reported that polyfunctional oxetane monomers having a plurality of oxetanyl groups in one molecule which are 4-membered cyclic ethers have photo-curability equal to or higher than the corresponding polyfunctional epoxides ("Journal of Macromolecule Science", Vol. A29, No. 10, Page 915, 1992; Vol. A30, Nos. 2 & 3, Page 173, 1993; Vol. A30, Nos. 2 & 3, Page 189, 1993). Furthermore, photo-curing compositions mainly composed of polyfunctional oxetane monomers are also proposed (JP-A-6-16804).
Ultraviolet-curing resins obtained using these polyfunctional oxetane monomers have the characteristic that ultraviolet-curing rate thereof is much higher than that of epoxy resins.
However, although high curing rate is an important feature in photo-curing resins, it is also necessary that properties of cured products are superior. Photo-curing resins using oxetane compounds which have been hitherto reported are inferior in properties of the coat after cured to those mainly composed of epoxy resins. Therefore, photo-curing resins having oxetanyl groups as polymerizable groups have a rapid photo-curability, but can hardly be applied to the uses which require characteristics such as adhesion and elongation.